It is becoming increasingly popular to use various types of mechanical equipment to pick tobacco, to transport picked tobacco in bulk form and to cure tobacco in bulk form by forced air. In the picking of tobacco, several acceptable tobacco harvesters are available, such as that disclosed in Long, U.S. Pat. No. 3,834,137 and Applicant's U.S. patent application Ser. No. 912,428 U.S. Pat No. 4,192,124. In handling the tobacco leaves for purposes of cure, several advances have been made over the customary tying of tobacco leaves to a stick. An example involves the use of tobacco racks, such as that disclosed in Wilson, U.S. Pat. No. 3,083,517. Recently, the principle of tobacco curing using racks has been improved upon by the development of bins which provide for the forced air cure of tobacco in contained bulk form. Examples of such types of bins are disclosed in Long, U.S. Pat. No. 3,834,137 and subsequent U.S. Pat. No. 3,935,959.
Several developments have been made in the design of a kiln for use in curing tobacco. The most significant advance is in the forced air cure of tobacco involving low profile kilns having a plenum beneath the floor which forces air upwardly through the racked or contained bulk form tobacco leaves to effect a cure under controlled humidity and temperature conditions. An example of such kilns is disclosed in Long, U.S. Pat. No. 3,834,137. Not all forced air systems, however, have a plenum, because the structure is completely opened at the bottom where the racks are supported above kiln base. Rather extensive crane arrangements have been used in association with such kilns to effect positioning of these very heavy containers and racks in kilns. Such crane systems may be that shown in Long, U.S. Pat. No. 3,834,137, which requires the location of a heavy beam extending the length of the ceiling of the forced air kiln.
To avoid the use of cranes in loading the bins, or bulk form containers in the kiln, the bins may be provided with wheels on their base, such as in Long, U.S. Pat. No. 3,834,137. The wheels ride on rails located on each side of the kiln to permit rolling of the loaded bin into position. This however, has the significant drawback in that the rollers on the bins, as used in the field, are exposed and subject to damage. Further, in rolling these very heavy bins into the kiln, as they extend the width of the kiln, requires a great deal of effort and in instances where such bins have open bottoms, the leaves are free to drag and become caught in the rails which can further hamper the ease with which the bin may be inserted in the kiln.
A further drawback with containers which have completely open bottoms is that with perforated kiln floor panel designs, the leaves are free to drag on the panels and, therefore, are free to clog the perforations in the floor which can hamper kiln cure effectiveness.
With the open design for kiln floors, reliance is placed on sealing between containers and sealing between container and kiln walls to ensure an upward flow of air through the contained bulk cure form of leaves. There is, therefore, a significant problem with misaligned containers not providing the proper seal, due to sloppy fit of rollers on track or presence of foreign material between contacting bin edges. Sealing flaps along kiln walls may lose their posture, thereby not forming a seal with container edge. A free flow of air is allowed to move through these unsealed areas, thereby reducing the amount of air flowing through the containers resulting in an uneven cure of the tobacco in the kiln and may in some instances spoil a substantial amount of the bulk form tobacco. This arrangement, therefore, substantially reduces the efficiency of forced air kilns.
An additional problem in relying on alignment between abutting surfaces of containers to provide a seal is that over time with usage, some of the containers can become warped their sealing edges damaged, or with the very long narrow type of container, the top plate, which abuts a top plate of other containers such as disclosed in Long, U.S. Pat. No. 3,834,137, tend to bow. As a result, spaces will form between container sealing areas. These aspects, therefore, further contribute to inefficiency of forced air kilns. Further, the use of wheels which elevate containers above a kiln floor permit the air to travel in any direction on emerging upwardly through the floor. The air will seek a path of least resistance to upward movement, whether it be an unsealed area of the containers or a container which has developed a channelling problem to thereby decrease the efficiency of the cure. Conditioning is another consideration which cannot be accomplished with containers on wheels, because if one or more of the bins are removed from the kiln, conditioning cannot be continued for the remaining bins since the air will now travel freely through the open space. This presents a problem when it is not possible to transfer all tobacco from the kiln to the stripping room for grading and bailing within a period which will maintain the desired moisture content in the tobacco remaining in the kiln. Therefore, it is desirable to either provide apparatus to expedite removal of conditioned tobacco from a kiln before it commences drying out again, or provide a kiln floor which would permit conditioning of containers remaining in the kiln while some have already been removed.
In an attempt to achieve a better distribution of leaves in containers, it was proposed by Canadian Tobacco Research Group, as reported in the Canadian Tobacco Growers July, 1978, that the container for use in bulk cure of leaves be hinged at its mid-portion to provide two sections which may be folded towards one another and held closed after fill. This results in filling container sections of lesser depth, so that a more uniform density of leaves may be attained in the container.
A further drawback with containers for bulk cure of tobacco is that it usually requires an individual present at the rear of the mechanical harvester to ensure a uniform distribution of leaves within the container. Also, such containers have smooth sidewalls so that when positioned in the kilns, the forced air may readily pass upwardly along the smooth sidewalls, where there is a lesser density of leaves resulting in channelling. Such channelling can have a very undesirable effect on the cure of tobacco in the immediate area, such as premature greening and in areas of the container where less air flows, there can be stem rot and swell stems which spoil that portion of the tobacco.
An additional drawback of bulk form containers is the fact that the corners in the containers are square and, due to the natural resiliency of the leaves when placed in the container, a lighter density of leaves occurs in the corners which again contributes to channelling within the containers when positioned in a kiln. Such containers are also costly to manufacture, involving several welding operations to attach sidewalls to bottom walls. Also a rather loose arrangement has been provided for spike members which hold the bulk form leaves in position, such as that referred to in Long, U.S. Pat. No. 3,935,959. That spiking arrangement relies on the pins passing through a screen intermediate of the container to hold them in position and ensure proper securement.
It is, therefore, an object of this invention to provide a system for handling and curing tobacco which overcomes or avoids a number of the above problems.